I am using 3com POE injectors behind a gigabit switch, the POE injector is a 10/100 device and my phones are 10/100/1000, the phones will NOT link up. When I remove the POE injector from the equation, and use "wall wart" transformers to power the phones, all is good, phones link and talk to my VOIP PBX and the world! Anyone run into this before? Any solution or ideas?

What phones? What PoE standard (or non-standard) do they support? What is the voltage on the PoE injectors?

For instance, Polycom SIP IP501 use a proprietary pinout so you can't use a 802.3af compliant PoE injector. Have to use their cable or make your own. If I am not mistaken.

The other possible issue, have you tried forcing the port speed on the phones and/or switch?

Thanks Hawk, I am using Polycom P560 and P670's, they power up just fine via the POE injector, but will not link. I am checking on the POE injector at the ccom site now, and I have the manual on the Polycon phones so will check. I'll let you know the outcome.

Does the phone have the option to force the connection to 100Mb?

Polycom is usually 24VDC, non-standard (i.e. not 802.3af) PoE, on unused pairs.

You can't use a standard PoE injector with those. Even if they come up, they won't link because the data pairs are not isolated enough. (IEEE standard PoE runs the power on the same pairs with data, and capacitively couples the data through to the device.)

Any device that is truly 10/100/1000 should have no problem selecting 10/100 when talking to your PoE injectors. The weak part of auto negotiation is the duplex selection, NOT speed (clock speed is easy to detect.)